It can be done but I personally dont like dual booting. There always seems to be problems that you can live without.
I use hard disc caddies and have a hard disc for each OS. That way I have never have any nasties. The caddies are not so expensive at Maplins.
It is also good to have it this way because if you pick up a virus inspite of all your precautions you still have another setup to be working with.
No doubt other people will strongly dissacgree with me, but that's life.